SELANGOR remains a hotspot for dengue outbreaks and cases , with a cumulative of 37,545 dengue cases registered in 2022 , an increase of 21,804 ( 138.5 per cent ) cases compared to 2021 .

And for 2023 , according to the State Public Health , Unity , Women and Family Development Committee Chairman , Dr Siti Mariah Mahmud , Selangor is expected to see a 150 per cent increase in dengue cases if Aedes mosquito breeding sites are not dealt with seriously by the community .

A total of 6,870 cases had been reported as of Feb 11 , the sixth epidemiological week ( EW ), an increase of 141.4 per cent from last year . And 510 dengue outbreak localities were detected , an 8.5 per cent rise from the 470 localities reported the week prior .

The Petaling district recorded the highest number of localities at 203 , followed by Hulu Langat ( 120 ), Klang ( 82 ) and Gombak ( 69 ).

Public Health Specialist Dr Sukhvinder Singh Sandhu from the Vector Borne Disease Control Unit of Selangor State Health Department said dengue outbreaks are being seen in all the districts in Selangor .

“ However , most outbreaks are recorded in Petaling , Hulu Langat , Klang and Gombak districts because these districts are more urbanised and densely populated than other districts in Selangor .

“ These outbreaks are reported

to occur in localities with poor maintenance of the environment surrounding the premises with many breeding sites found indoors and outdoors . This can be associated with the lack of civic-mindedness in certain pockets of the communities in maintaining cleanliness .”

CONTRIBUTING FACTORS

Apart from the usual factors such as environmental cleanliness , climate change and poor civic-mindedness , Selangor ’ s rise in dengue cases is also contributed by the following factors : a . The spread of the dengue virus is also associated with increased mobility , especially following Covid-19 movement restriction upliftment . As Selangor is a densely populated state , the upliftment of the movement restriction has seen human movement in Selangor back to the pre-pandemic era .

As movement increases , the possibility of an infected person in the viraemic stage ( virus still in the blood ) spreading the infection increases as there are higher chances of Aedes mosquitoes biting him and transmitting the virus to another person it bites . b . Circulating dengue virus serotype also influences the rise of dengue cases . The four dengue virus ( DENV ) serotypes are closely related but distinct . The change

c .

d .

in the circulating dengue virus serotype can lead to the rise of dengue infection as the community immunity towards the new circulating serotype is low / partial . Currently , the predominant circulating dengue virus serotype in Selangor is DENV-4 . Selangor is a very urbanised and densely populated state . Rapid and unplanned urbanisation with inadequate solid waste management provides favourable conditions for the mosquitos to breed and spread the dengue virus . The design of some buildings that promote semi-permanent areas for Aedes breeding , leading to an upsurge in dengue cases . Some of the design issues identified at highrise buildings are unreachable rain gutters that makes checking and cleaning difficult for residents , poor drainage and piping system , gully trap designs and uneven

surface of the floors and concrete rooftops , resulting in water stagnation and breeding sites . As dengue outbreaks are related to the cleanliness of the premises and the surroundings , communities must impart self-discipline to maintain their premises and surroundings free from Aedes mosquitoes and breeding sites .

Dr Sukhvinder explained that the need to destroy breeding sites arises as Aedes mosquitoes demonstrate transovarial transmission capabilities .

“ The infected female Aedes mosquito can transmit the dengue virus to its eggs , which will develop into infectious larvae and subsequently become Aedes mosquitoes .

“ These mosquitoes can readily transmit the dengue virus to humans when they bite . As such , the dengue virus transmission in a locality will continue to spread if these mosquito breeding habitats are not destroyed .”

VACCINE development for dengue is a very challenging task owing to the distinct characteristics of the four serotypes ( DENV-1 , DENV-2 , DENV-3 & DENV-4 ), geographical distribution and the need to evaluate all four serotypes against the vaccine candidate , said Dr Tahir Aris , the Director of Institute for Medical Research ( IMR ).

“ Antibody-dependent enhancement ( ADE ) is another pathophysiological phenomenon that must be considered when developing a safe and effective tetravalent dengue vaccine .

“ Currently , IMR ’ s main focus for dengue therapeutics is developing antiviral products / candidates which can help prevent deterioration of dengue patients .”

The Virology Unit , under IMR ’ s Infectious Disease Research Centre ( IDRC ), conducts numerous studies to fill the gaps and consider the current demand to combat dengue in Malaysia .

Apart from the dengue therapeutics , the Virology Unit has also researched : 1 . Testing in-vitro and in-vivo antiviral activities ( e . g ., drug repurposing , natural products ) against the dengue virus .

2 . New ventures into the development of anti-dengue peptides . For pre- and postinfection treatments of DENV infections “ We have also developed a network of partners , including the Drugs for Neglected Diseases Initiative Programme ( DNDi ) and public universities . We are always open to

collaboration and participation in dengue vaccine development / clinical trials , assessing the benefits and drawbacks ,” said Dr Hj Tahir .

He also suggested a roundtable discussion for clinicians and researchers , including those from universities , to address the dengue research gaps and integrate research from both vector control and disease pathophysiology aspects .

“ What the physicians would like to understand about the disease should match what the researchers can offer to reduce the burden of infection , hospitalisation , and severity . This would highlight the most recent research priority topics and guarantee that research funding is used more effectively .”

SHIFT IN THE TREND OF DENGUE SEROTYPES

The role of IDRC ’ s Virology Unit in addressing the dengue epidemic in Malaysia is not limited to just dengue treatment and drug research but also includes dengue diagnostic testing , pathogenesis and epidemiological and serotype surveillance .

For serotype surveillance , he shared : “ The Virology Unit actively conducts routine molecular diagnostic testing for the serotyping and identification of dengue virus in patient samples .

“ The state hospitals provide us samples , such as blood , serum , CSF , and biopsies , from patients whose NS1 positivity has been determined by a rapid antigen test or to rule out dengue in forensic cases .

“ The States of Kedah , Johor , Melaka , Selangor and Federal Territory Kuala Lumpur have provided a significant number of samples over the previous three years for the routine diagnosis of dengue , according to our data .”

He continued : “ We also employ an in-house multiplex Real-Time rt-PCR assay for detecting and serotyping all four dengue serotypes . Within each dengue serotype , genotypes are usually linked to geographical locations .

“ Dengue serotyping is essential to monitor the serotype shift . A shift in the trend of dengue serotypes may contribute to the accelerating number of dengue cases due to the difference in severity or ADE or lack of immunity against the dominant dengue serotype / genotype .

“ The four dengue serotypes are genetically related but antigenically distinct . Although DENV-2 is generally acknowledged as the most virulent serotype , it must be noted that host characteristics , including immune response , age , and co-morbidities ,

also increase the severity of dengue infection . It is crucial to monitor the circulation trend of the serotypes via dengue serotype surveillance .”

“ The dengue serotype surveillance has been carried out in Malaysia on a timely basis . In the Virology Unit , samples from dengue patients admitted to MoH facilities are referred to the IMR to determine dengue serotype .

“ While the National Public Health Laboratory , Sungai Buloh established a dengue serotype sentinel surveillance to monitor changes in the dengue serotype domination over time .

“ By sending weekly reports to the MoH ( Serotype distribution vs locale ), which are combined with reports from other institutions that carry out the serotyping test , we contribute to the serotype surveillance data .”

This dengue serotype surveillance data is important , and the data can be inferred to predict dengue outbreaks in localities and plan appropriate responses , he said . – The Health